3 Piece Cylinder Airlock with Universal Blue 6.5 Gallon Carboy Cap

Great product-fits a 6.5 gallon threaded-neck (acid) carboy snugly enough that I could pressure transfer to a keg with about 2 pounds of pressure (I would not recommend that, but I did it anyway). I would buy again if I needed another.

I did eventually get it on the carboy after SEVERAL attempts, finally getting it over the lip gently starting on one side and sliding the opposite side down the edge of a VERY slim and narrow blade angled outward, because it wouldn't ever go over the lips on its own. It's been down there a week. I'm afraid to touch it, definitely not stable - but I'm hoping the cap will stretch a little with repeated use. Outside of that - the concept looks good.

The air lock is an added benefit I guess...didn't really need it though.

These provide a nice tight fit on my 6.5 gallon carboys. I have the carboys with the smooth (not ribbed) sides if that helps.

You claim that it’s supposed to fit a 3 to 5 gallon car boy but it doesn’t I literally had to sand and grind rubber away on the inside so that I could get it to work. I would have sent them back but I needed something very bad because I made about 10 gallons of grape wine and I had no substitute